Gooseberry bush problem - not sawfly

I'm guessing this is some sort of virus or fungus causing the problem. The leaves appear healthy i.e. no marks or powdery appearance, before they wilt. Initially it was only one branch but now it appears to have spread to others on the same bush, albeit some branches still look very healthy. The fruit appears to be ripening OK. The bush did have some sawfly earlier in the season but this was dealt with by by a mixture of squeezing the caterpillars and lightly spaying with Bugclear (approved for fruit bushes)

What is the best course of action?

1. Will the affected branches recover (there is some hint of tip growth being less affected)?

2. Is there a treatment?

3. Should I cut out the affected branches.

4. Should I grub out the whole bush in case it spreads to the other three very healthy ones?

Is this a previously healthy and fruiting bush, or is it a young one? If the latter, some individual plants (of any variety or species) are just not very strong and it's just a part of nature - don't waste effort on them.

Thanks for your interest - This is a mature, usually heavy fruiting bush. We have suffered with sawfly in the past, but this years attack was minor in comparison. This leaf wilt is something completely new to me.

Broomcupboard did you have a bad sawfly problem last year? And maybe the year before too?

A severe sawfly attack does weaken the bushes and if you lost leaves these past two summers it may be the cause of your ailing plant. I would try to do something this autumn ...like a winter oil wash. Tar oil was the traditional treatment but now not available I think...not sure??